1. Field of the Invention
The present invention relates to a conical bearing apparatus. More particularly, the present invention relates to a conical bearing apparatus having a dynamic pressure generating groove on the upper section of a conical bearing in order to increase a fluid pressure generated by the other dynamic pressure generating groove formed on the tapered surface of the conical bearing.
2. Description of the Related Art
Recently, as the computer-related industries have developed, driving motors for various kinds of devices, such as an optical polygon driving apparatus of a laser printer, a spindle motor of a hard disk, or a head driving motor of a VCR, are required to have high accuracy and superhigh rotation performance without any trembling or vibration of the axis of the apparatus. In response to the demand to eliminate the trembling and vibration of the axis which degenerates the performance of the devices, driving motors capable of being stably rotated at a high speed have been developed, and moreover, a fluid bearing apparatus which rotates the axis of rotation of the driving motor precisely and speedily has been developed.
The above-described fluid bearing apparatus has dynamic pressure generating grooves which generate the dynamic pressure. Dynamic pressure generating grooves are mainly used as follows: a dynamic pressure generating groove having a spiral shape in a thrust bearing for supporting a thrust load; and a dynamic pressure generating groove having a herringbone shape in a radial bearing for supporting a radial load.
Generally, the conical bearing apparatus, which is used in an optical polygon driving apparatus of a laser printer, includes a conical bearing fixed at one end of the axle of fixation; and a bush formed apart from the conical bearing at a predetermined distance for receiving the conical bearing. Accordingly, the optical polygon support connected to the bush faces the upper section of the cone. Moreover, on the tapered side of the cone, a dynamic pressure generating groove is formed. When the bush which is connected to the optical polygon support starts to rotate, fluid flows into the dynamic pressure generating groove of the cone which is facing the conical groove of the bush, thereby generating a dynamic pressure. This dynamic pressure influences the optical polygon support facing the upper section of the cone, and enables the body of rotation to be risen.
In order to minimize the time when the fluid pressure generated by the dynamic pressure generating groove is more than the weights of the bush, optical polygon and optical polygon support, it is necessary to properly design the number and the area of the dynamic pressure generating grooves. However, in the conventional conical bearing apparatus, forming the dynamic pressure generating groove only on the tapered side of the cone is insufficient.
Accordingly, as it takes a long time for the body of rotation, such as the bush, to rise from the cone, an excessive friction between the conical bearing and the body of rotation is generated, thereby causing instability in rotating the axis.